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PubMed1998

Muscles within muscles: the neuromotor control of intra-muscular segments.

The aim of this investigation was to anatomically identify, and then determine the function of, individual segments within the human deltoid muscle. The anatomical structure of the deltoid was determined through dissection and/or observation of the shoulder girdles of 11 male cadavers (aged 65-84 years). These results indicate that the deltoid consists of seven anatomical segments (D1-D7) based upon the distinctive arrangement of each segment's origin and insertion. Radiographic analysis of a cadaveric shoulder joint suggested that only the postero-medial segment D7 has a line of action directed below the shoulder joint's axis of rotation. The functional role of each individual segment was then determined utilising an electromyographic (EMG) technique. Seven miniature (1 mm active plate; 7 mm interelectrode distance) bipolar surface electrodes were positioned over the proximal portion of each segment's muscle belly in 18 male and female subjects (18-30 years). EMG waveforms were then recorded during the production of rapid isometric shoulder abduction and adduction force impulses with the shoulder joint in 40 degrees of abduction in the plane of the scapula. Each subject randomly performed 15 abduction and 15 adduction isometric force impulses following a short familiarisation period. All subjects received visual feed back on the duration and amplitude of each isometric force impulse produced via a visual force-time display which compared subject performance to a criterion force-time curve. Movement time was 400 ms (time-to-peak isometric force) at an intensity level of 50% maximal voluntary contraction. Temporal and intensity analyses of the EMG waveforms, as well as temporal analysis of the isometric force impulses, revealed the neuromotor control strategies utilised by the CNS to control the activity of each muscle segment. The results showed that segmental neuromotor control strategies differ across the breadth of the muscle and that individual segments of the deltoid can be identified as having either "prime mover", "synergist", "stabiliser" or "antagonist" functions; functional classifications normally associated with whole muscle function. Therefore, it was concluded that the CNS can "fine tune" the activity of at least six discrete segments within the human deltoid muscle to efficiently meet the demands of the imposed motor task.

Adult↗
PubMed1987

High-risk subgroups of patients with non-Q wave myocardial infarction based on direction and severity of ST segment deviation.

To determine the significance of the direction of ST segment deviation on admission of patients who evolved non-Q wave myocardial infarction (MI), 97 patients with initial ST segment depression were compared to 207 patients with initial ST segment elevation. Patients with ST segment depression developed smaller infarcts than those with ST segment elevation (creatine kinase MB isoenzyme 8.2 vs 13.3 gmEq/m2, p less than 0.002), but had a lower left ventricular ejection fraction on admission (44% vs 51%, p less than 0.001), more in-hospital complications, and a higher cumulative 1-year mortality (29% vs 11%, p less than 0.001) that could be accounted for by an excess of adverse baseline characteristics. Although a severity index (combining magnitude and extent of the initial ST segment deviation) was not useful for discriminating prognosis of patients with non-Q wave MI who presented with ST segment depression, it was useful in identifying a subgroup of patients with ST segment elevation with an adverse prognosis. The poor outcome of patients with non-Q wave MI presenting with either ST segment depression or severe ST segment elevation on admission suggests that patients in these subgroups should receive close surveillance and should possibly be considered for aggressive therapy.

Electrocardiography↗
PubMed1984

Angiographic evidence that reciprocal ST-segment depression during acute myocardial infarction does not indicate remote ischemia: analysis of 23 patients.

Although reciprocal ST-segment depression from the remote noninfarcting ventricular wall during acute myocardial infarction (MI) is a common clinical finding, the significance of this electrocardiographic pattern is unclear. Previous retrospective studies have suggested that these findings may reflect either remote wall ischemia, multivessel coronary artery disease (CAD), extensive MI or a benign electrical phenomenon. Prior studies have lacked angiographic data obtained at the time of these acute electrocardiographic changes. In this study we prospectively evaluated 23 patients with acute MI. Left ventricular wall motion, coronary anatomy and the ECG were all assessed over a short period during the acute phase of the MI. Segmental wall motion was used as a sensitive indicator of ischemia. Seventeen patients had acute anterior MI, of whom 47% had reciprocal ST-segment depression; 6 patients had inferior MI, with 3 showing reciprocal ST depression. The mean degree of ST-segment elevation from the infarcting wall tended to be greater in patients with reciprocal ST-segment depression than in those without such reciprocal ST depression (2.8 +/- 0.4 vs 1.9 +/- 0.3 mm, p = 0.06). Patients with and without reciprocal ST-segment depression had similar degrees of segmental dysfunction in the infarct wall. However, no abnormalities in segmental wall motion in the remote wall were seen regardless of the presence or absence of remote wall ST-segment depression. In addition, the presence or absence of ST-segment depression did not predict the extent or degree of CAD.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Holter monitoring before, during and after percutaneous transluminal coronary angioplasty for evaluation of high-resolution trend recordings of leads CM5 and CC5 for ST-segment analysis.

Frequency-modulated Holter monitoring of leads CM5 and CC5 was performed before, during and after percutaneous transluminal coronary angioplasty (PTCA) in 16 patients with stenosis of the left anterior descending coronary artery, in 5 patients with stenosis of the left circumflex coronary artery, and in 5 patients with stenosis of the right coronary artery. All patients presented with 1-vessel coronary artery disease and stable or unstable angina pectoris. ST-segment analysis was based on high-resolution trend recordings. During balloon inflations all patients had significant (at least 0.1 mV) ST-segment changes in lead CM5. In lead CC5, associated ST-segment deviations were found in 22 of 26 patients. During 29.2 +/- 13.6 hours before PTCA, 90 spontaneous episodes with significant ST-segment deviations were detected in 10 patients. Of these episodes, 17% were characterized by ST-segment deviations in lead CC5 only, 57% by ST-segment deviations in lead CM5 only, and 27% by simultaneous ST-segment deviations in both leads. Asymptomatic episodes occurred twice as frequently as symptomatic episodes (66 vs 34%). Symptomatic episodes were more often characterized by ST-segment deviations of at least 0.15 mV (48 vs 9%, p less than 0.001) and by ST-segment deviations observed in both leads simultaneously (48 vs 15%, p less than 0.001). During 34.8 +/- 10.6 hours after successful PTCA, 5 spontaneous asymptomatic episodes with significant ST-segment deviations were detected in 2 patients.

Adult↗
PubMed1976

The structure and stability of trypsin-resistant segments from rabbit tropomyosin.

Tropomyosin was found to undergo only limited digestion by trypsin at 0 degrees C and the two segments that accumulated amounted to two-thirds of the original protein. They are referred to as segments A and B. These segments were not resistant to trypsin digestion at 20 degrees C and at the latter temperature no large fragments remained as judged by disc gel electrophoresis. Segments A and B were separated from each other on the basis of solubility differences and were found to have molecular weights of 24600 and 21900 respectively. Each of the segments appeared to retain about 70-75% of the helical conformation as judged by circular dichroism at 20 degrees C. However, the segments did not show any of the inhibitory activity of the parent tropomyosin molecule when mixed with troponin in the Mg2+-actomyosin ATPase system. Amino acid analysis showed that the portion of tropomyosin that was digested by trypsin (EC 3.4.21.4) had a lower content of the helix stabilizing residues Glu and Leu and a higher content of the helix-destabilizing residues Arg and Lys. These differences indicate that the digested portion should be less stable in the helical conformation than the two trypsin-resistant segments. End group determinations along with the results of the amino acid analysis indicated that segment A was probably derived from the central one-third of tropomyosin and segment B from the C-terminal one-third. By the process of elimination the N-terminal third appears to have been more liable region that was digested by trypsin. The segments A and B were shown to differ in their stability to denaturation by guanidine-HCl and elevated temperature. All of these observations indicate that tropomyosin is not a uniform structure and is composed of regions of different stability.

Adenosine Triphosphatases↗
PubMed1987

EEG alpha map series: brain micro-states by space-oriented adaptive segmentation.

The spontaneous EEG, viewed as a series of momentary scalp field maps, shows stable map configurations (of periodically reversed polarity) for varying durations, and discontinuous changes of the configurations. For adaptive segmentation of map series into spatially stationary epochs, the maps at the times of maximal map relief are selected and spatially described by the two locations of maximal and minimal (extreme) potentials; a segment ends if over time an extreme leaves its pre-set spatial window. Over 6 subjects, the resting alpha EEG showed 210 msec mean segment duration; segments longer than 323 msec covered 50% of the total time; the most prominent segment class (1.5% of all classes) covered 20% of total time (prominence varied strongly over classes; not all possible classes occurred). Spectral power and phase of averages of adaptive and pre-determined segments demonstrated the adequacy of the strategy, and the homogeneity of adaptive segment classes by their reduced within-class variance. It is suggested that different segment classes manifest different brain functional states exerting different effects on information processing. The spatially stationary segments might be basic building blocks of brain information processing, possibly operationalizing consciousness time and offering a common phenomenology for spontaneous activity and event-related potentials. The functional significance of segments might be modes or steps of information processing or performance, tested, e.g., as reaction time.

Adult↗
PubMed1979

The structure of A segments from glycerinated skeletal muscle.

The A band of skeletal muscle consists of an array of thick myosin-containing filaments along with non-myosin proteins such as C protein and M line protein. In order to study the arrangement of the myosin and non-myosin components, A segments which are aggregations of thick filaments held together at the M line were prepared from glycerinated chicken pectoral and rabbit psoas muscles and examined by electron microscopy. Details of the preparative technique and comparison of the morphologies of A segments and I segments are provided. The A segments from chicken pectoral muscle exhibited 11 to 12 stripes in each half lateral to the bare zone. Several less distinct bands as well as subdivisions of the individual stripes were also observed. The periodicity of the major stripes in the A segments was 424 +/- 10 A. The A segments prepared from rabbit psoas muscle had a periodicity of 432 +/- 13 A, but in contrast with chicken A segments, fewer rabbit A segments showed this periodicity. We conclude that A segments can be separated from glycerinated chicken and rabbit skeletal muscles and compare our results with those of others who prepared A segments from frog and rabbit skeletal muscles in the absence of glycerol.

Animals↗
PubMed1984

Bacteriophage P1 carries two related sets of genes determining its host range in the invertible C segment of its genome.

The bacteriophage P1 genome carries an invertible C segment consisting of 3-kb unique sequences flanked by 0.6-kb inverted repeats. Host range mutations of P1 have been mapped in the C segment region. P1 derivatives carrying insertions and deletions in the left half of the C segment in one of two orientations termed C(+) do not affect the plaque-forming ability on Escherichia coli K12 and E coli C, whereas those having insertions in the right half of the C segment fail to form plaques on these hosts. An E. coli C mutant which allows the latter insertion mutants with the C segment in the C(-) configuration to form plaques has been isolated. Not only P1 C(-) but also P1 C(+) phages gave plaques on this E. coli C mutant. The results are consistent with the notion that the C segment of P1 carries two sets of genes for host specificity, and that C inversion alters the P1 host range through activation of one set of the genes. Furthermore, extended host range mutants can be isolated by point mutation in either set of the P1 genes. C inversion is a slow process, but it occurs on the phage genome upon its vegetative growth as well as on the prophage in the lysogenic state. The 3-kb invertible G segment of the phage Mu genome is known to be homologous with the central 3-kb part of the C segment of P1 and to carry also two sets of genes for Mu host specificity. While only Mu G(-) grows on E. coli C, both Mu G(+) and Mu G(-) phages form plaques on the E. coli C mutant sensitive to P1 C(-). In the discussion the gene organization of the P1 C segment is compared with that of the Mu G segment.

Coliphages↗
PubMed1990

Coding properties of the S and the M genome segments of Sapporo rat virus: comparison to other causative agents of hemorrhagic fever with renal syndrome.

Three serologically distinct groups of hantaviruses have been associated with severe, moderate, and mild forms of hemorrhagic fever with renal syndrome (HFRS). To gain a better understanding of the genetic variation among these viruses, we cloned and sequenced the M and the S genome segments of Sapporo rat virus, an etiologic agent of moderate HFRS, and compared the predicted gene products to those of Hantaan virus, and the Hällnäs strain of Puumala virus, which are etiologic agents of severe and mild HFRS, respectively. The SR-11 S segment consisted of 1769 nucleotides and had an open reading frame (ORF) in the virus-complementary sense RNA with a coding capacity of 429 amino acids. Deduced amino acids from the SR-11 S segment ORF displayed 83% homology with those of Hantaan nucleocapsid (N) protein. Comparison of the S segment ORFs of all three viruses revealed 58% homology. No evidence for additional nonstructural protein(s) encoded by the SR-11 S segment was obtained. The SR-11 M segment consisted of 3651 nucleotides and had an ORF in the virus-complementary sense RNA with a coding capacity of 1134 amino acids. Amino acid sequences predicted from the SR-11 M segment ORF were 75% homologous with those encoding Hantaan G1 and G2 envelope glycoproteins. Comparison of the deduced amino acid sequences of the M segment ORFs of SR-11, Hantaan, and Hällnäs viruses revealed a 43% homology for amino acids constituting the G1 proteins and a 55% homology for amino acids constituting the G2 proteins of the three viruses. The envelope proteins of SR-11 virus were localized within the M segment ORF by amino-terminal sequence analysis of purified G1 and G2. G1 initiated at amino acid 17 and G2 at amino acid 647 within the ORF. Five potential asparagine-linked glycosylation sites were identified in the SR-11 G1 coding sequences, four of which were conserved between Hantaan and SR-11 viruses and three of which were conserved among all three viruses. One potential glycosylation site was identified in the SR-11 G2 coding sequences and was conserved among Hantaan, SR-11 and Hällnäs viruses. Cysteine residues were highly conserved within the M segment ORFs of all three viruses, suggesting a similar structure and function of the G1 and G2 proteins.

Amino Acid Sequence↗
PubMed1990

Differential enhancement of postischemic segmental systolic thickening by diltiazem.

Prolonged depression of segmental systolic thickening after brief coronary artery occlusion may result principally from events during reperfusion rather than during the ischemic interval. Thus, cellular calcium overload at reperfusion may be a mediator of contractile dysfunction after brief ischemia, and reduction of calcium entry by diltiazem, a calcium channel antagonist, may enhance recovery of systolic thickening after brief periods of ischemia. Thirteen awake unsedated dogs instrumented with hemodynamic catheters, left anterior descending coronary artery occluders and five to six pairs of intramyocardial sonomicrometers underwent two 15 min coronary artery occlusions with 24 h reperfusion. The order of infusion of diltiazem (15 micrograms/kg per min) or saline solution was alternated. Systolic thickening, hemodynamic variables and regional myocardial blood flow were measured serially over 24 h. Despite equally severe ischemic dysfunction during coronary occlusion, diltiazem-treated segments with systolic thinning during ischemia recovered control segmental thickening significantly earlier than saline solution-treated segments (at 30 versus 180 min of reperfusion). Blood pressure was mildly decreased during diltiazem treatment; therefore, a second group of 10 dogs underwent a similar occlusion and reflow period during infusion of nitroprusside to lower mean arterial pressure equivalently. Decreases in blood pressure in this group resulted in some improvement in segmental systolic function; however, this did not reach statistical significance at any time. Regional myocardial blood flows were similar in the saline solution- and diltiazem-treated groups during ischemia and reflow. Thus, it is concluded that 1) diltiazem infusion significantly enhanced recovery of segmental systolic thickening after 15 min of ischemia and 24 h of reperfusion; 2) the enhancement in segmental systolic function could not entirely be attributed to decreased mean arterial pressure; 3) improvement in postischemic segmental ventricular function was seen only in those segments with systolic thinning during ischemia; thus, segments with the most severe ischemic dysfunction benefited most; and 4) there were no important differences in regional myocardial blood flow during ischemia and reperfusion between saline- and diltiazem-treated animals.

Animals↗
PubMedDate not supplied

Segmentation of images of skin lesions using color and texture information of surface pigmentation.

Image segmentation algorithms extract regions on the basis of similarity of a predefined image feature such as gray-level value. In many applications, images that exhibit a variety of structure or texture cannot be adequately segmented by gray-level values alone. Additional features related to the structure of the image are needed to segment such images. Images of skin lesions exhibit significant variations in color hues as well as geometrical appearance of local surface structure. For example, images of cutaneous malignant melanoma exhibit a rich combination of color and geometrical structure of pigmentation. In these images, the local repetition of the geometrical surface structure provides the basis for the appearance of a texture pattern in the neighborhood region. For obtaining meaningful segmentation of images of skin lesions, a multichannel segmentation algorithm is proposed in this paper which uses both gray-level intensity and texture-based features for region extraction. The intensity-based segmentation is obtained using the modified pyramid-based region extraction algorithm. The texture-based segmentation is obtained by a bilevel shifted-window processing algorithm that uses new generalized co-occurrence matrices. The results of individual segmentations obtained from different channels, representing the complete set of color and texture information, are analyzed using heuristic merging rules to obtain the final color- and texture-based segmentation. Simulated as well as real images of skin lesions, representing various color shades and textures, have been processed. We show that using contrast link information in the pyramid-based region extraction process, and using the absolute magnitude and directional information in the generalized co-occurrence matrices (GCM) method, significant improvement in image segmentation can be obtained. Further, by incorporating the merging rules better results are obtained than those obtained using the gray-level intensity feature alone.

Algorithms↗
PubMed2006

Joint registration and segmentation of neuroanatomic structures from brain MRI.

RATIONALE AND OBJECTIVES: Segmentation of anatomic structures from magnetic resonance brain scans can be a daunting task because of large inhomogeneities in image intensities across an image and possible lack of precisely defined shape boundaries for certain anatomical structures. One approach that has been quite popular in the recent past for these situations is the atlas-based segmentation. The atlas, once constructed, can be used as a template and can be registered nonrigidly to the image being segmented thereby achieving the desired segmentation. The goal of our study is to segment these structures with a registration assisted image segmentation technique. MATERIALS AND METHODS: We present a novel variational formulation of the registration assisted image segmentation problem which leads to solving a coupled set of nonlinear Partial Differential Equations (PDEs) that are solved using efficient numeric schemes. Our work is a departure from earlier methods in that we can simultaneously register and segment in three dimensions and easily cope with situations where the source (atlas) and target images have very distinct intensity distributions. RESULTS: We present several examples (20) on synthetic and (3) real data sets along with quantitative accuracy estimates of the registration in the synthetic data case. CONCLUSION: The proposed atlas-based segmentation technique is capable of simultaneously achieve the nonrigid registration and the segmentation; unlike previous methods of solution for this problem, our algorithm can accommodate for image pairs having very distinct intensity distributions.

Algorithms↗
PubMed2005

Analysis of the interaction between segmental relaxation patterns and global diastolic function by strain echocardiography.

BACKGROUND: Strain echocardiography can depict segmental mechanical activity with high temporal and spatial accuracy, and may allow assessment of segmental relaxation not possible with conventional echocardiography. METHODS: Conventional and strain echocardiography were performed in healthy volunteers (young [group 1] and old [group 2]) and patients with normal 2-dimensional and stress echocardiography, with either normal global diastolic function (group 3a) or grade I or II global diastolic dysfunction (DD) (group 3b). Standard echocardiography criteria were used to define global DD. Early to late diastolic strain rate ratio less than 1.1 was defined as altered segmental relaxation. RESULTS: All participants had normal wall motion and ejection fraction. Participants of group 1 had normal segmental and global diastolic function. Participants of groups 2 and 3a demonstrated a wide range of altered segmental relaxation in the absence of global DD. All patients of group 3b had 12 or more segments with altered relaxation and global DD. Age and hypertension were associated with a larger number of altered segments, a lower mean early to late diastolic strain rate ratio, and global DD. CONCLUSIONS: A wide range of altered segmental relaxation can exist in the absence of global DD. Age and hypertension are associated with altered segmental relaxation and global DD. Assessment of segmental relaxation may be beneficial in the elderly and patients with hypertension.

Adult↗
PubMed2005

The sequence and phylogenetic analysis of avian reovirus genome segments M1, M2, and M3 encoding the minor core protein muA, the major outer capsid protein muB, and the nonstructural protein muNS.

The sequences and phylogenetic analyses of the M-class genome segments of 12 avian reovirus strains are described. The S1133 M1 genome segment is 2283 base pairs long, encoding a protein muA consisted of 732 amino acids. Each M2 or M3 genome segment of 12 avian reovirus strains is 2158 or 1996 base pairs long, respectively, encoding a protein muB or muNS consisted of 676 and 635 amino acids, respectively. The S1133 genome segment has the 5' GCUUUU terminal motif, but each M2 and M3 genome segment displays the 5' GCUUUUU terminal motif which is common to other known avian reovirus genome segments. The UCAUC 3'-terminal sequences of the M-class genome segments are shared by both avian and mammalian reoviruses. Noncoding regions of both 5'- and 3'-termini of the S1133 M1 genome segment consist of 12 and 72 nucleotides, respectively, those of each M2 genome segment consist of 29 and 98 nucleotides, respectively, and those of each M3 genome segment are 24 and 64 nucleotides, respectively. Analysis of the average degree of the M-class gene and the deduced mu-class protein sequence identities indicated that the M2 genes and the muB proteins have the greatest level of sequence divergence. Computer searches revealed that the muA possesses a sequence motif (NH(2)-Leu-Ala-Leu-Asp-Pro-Pro-Phe-COOH) (residues 458-464) indicative of N-6 adenine-specific DNA methylase. Examination of the muB amino acid sequences indicated that the cleavage site of muB into muBN and muBC is between positions 42 and 43 near the N-terminus of the protein, and this site is conserved for each protein. During in vitro treatment of virions with trypsin to yield infectious subviral particles, both the N-terminal fragment delta and the C-terminal fragment phi were shown to be generated. The site of trypsin cleavage was identified in the deduced amino acid sequence of muB by determining the amino-terminal sequences of phi proteins: between arginine 582 and glycine 583. The predicted length of delta generated from muBC is very similar to that of delta generated from mammalian reovirus mu1C. Taken together, protein muB is structurally, and probably functionally, similar to its mammalian homolog, mu1. In addition, two regions near the C-terminal and with a propensity to form alpha-helical coiled-coil structures as previously indicated are observed for each protein muB. Phylogenetic analysis of the M-class genes revealed that the predicted phylograms delineated 3 M1, 5 M2, and 2 M3 lineages, no correlation with serotype or pathotype of the viruses. The results also showed that M2 lineages I-V consist of a mixture of viruses from the M1 and M3 genes of lineages I-III, reflecting frequent reassortment of these genes among virus strains.

Amino Acid Sequence↗
PubMed2006

Manual fixation versus locking during upper cervical segmental mobilization. Part 1: an in vitro three-dimensional arthrokinematic analysis of manual flexion-extension mobilization of the atlanto-occipital joint.

BACKGROUND: Segmental manual spinal mobilization techniques are used to restrict the effects of interventions to one spinal segment. It is, however, not known whether it is possible to generate such a localization of effects. Segmental motion in the cervical spine was previously studied by applying pure moments of force on cadaver specimens. So far, no studies have been performed on the segmental three-dimensional (3D)-kinematic aspects of cervical manual flexion-extension mobilization. METHODS: 3D-aspects of manual flexion-extension motion in the atlanto-occipital and atlanto-axial segments were analysed in vitro using an electromagnetic tracking device. Segmental bony reference points were registered using a 3D-digitizing stylus to define bone-embedded coordinate frames. Six spinal specimens--five embalmed and one fresh--were analysed in this study. Segmental motions were analysed in the atlanto-occipital and the atlanto-axial joints during manual mobilization through the full range of flexion-extension mobility. The 3D-kinematic analysis of two different segmental mobilization techniques--manual fixation of C1 versus locking of the inferior cervical spine--is presented. RESULTS: A significant reduction (P<0.05) of the associated axial rotation and lateral bending motions was observed during the manual fixation technique without influencing the main motion component of flexion-extension. The locking technique did not significantly influence the movements on the mobilized atlanto-occipital segment, but reduced all movement components in the atlanto-axial joint. INTERPRETATIONS: The results suggest that, for manual segmental flexion-extension mobilization of the upper cervical spine, manual fixation or locking might be chosen in different situations according to the desired effects.

Atlanto-Occipital Joint↗
PubMed2006

The use of a segmented transducer for rib sparing in HIFU treatments.

The use of focused ultrasound as a minimally invasive treatment for tumours is rapidly expanding. Target organs include the liver and kidneys. Both single element and phased array transducers may be used in the clinic. The presence of the rib cage presents a problem in high intensity focused ultrasound (HIFU) treatment planning, due to its high attenuation of the HIFU beam resulting in a loss of power at the focus as well as an increase in the risk of damage at the rib and to overlying tissues, including the skin. In this paper, a linearly segmented transducer, in which all active elements are driven in phase, has been investigated. The aim of the study was to investigate how a beam with a clinically useful profile could be achieved by removing the contribution of edge segments from one side of the transducer to the field. We have considered the case in which the HIFU beam approaches the rib cage during a treatment and investigated configurations of the transducer for which up to three segments on the edge are switched off. This problem has been studied initially using a linear acoustic field program to model the segmented transducer's acoustic beam profile. Experimental measurements of the transducer's acoustic field were performed using an automated beam plotting system. Temperature measurements were made on a rib surface for two transducer configurations using a fine wire thermocouple. A thermochromic liquid crystal material was used to assess qualitatively the heating pattern generated by the ultrasound beam. We show the rib sparing potential of the segmented transducer during HIFU treatment by demonstrating a reduction in the prefocal width of the ultrasound beam when edge segments are switched off. This has been predicted with the acoustic field model and demonstrated experimentally by acoustic field measurements and observations of the heating pattern generated by the ultrasound beam. A significant decrease in the temperature rise on a rib was observed in the case for which three edge segments were switched off compared with when all segments were active. We conclude that a segmented transducer extends the potential for treating liver tumours. In the case where the tumour lies behind, but close to the edge of, the ribs, energy loss at the focus and excessive heating in the rib and overlying tissue can be avoided by switching off edge segments.

Acoustics↗
PubMed2006

even-skipped has gap-like, pair-rule-like, and segmental functions in the cricket Gryllus bimaculatus, a basal, intermediate germ insect (Orthoptera).

Developmental mechanisms of segmentation appear to be varied among insects in spite of their conserved body plan. Although the expression patterns of the segment polarity genes in all insects examined imply well conserved function of this class of genes, expression patterns and function of the pair-rule genes tend to exhibit diversity. To gain further insights into the evolution of the segmentation process and the role of pair-rule genes, we have examined expression and function of an ortholog of the Drosophila pair-rule gene even-skipped (eve) in a phylogenetically basal insect, Gryllus bimaculatus (Orthoptera, intermediate germ cricket). We find that Gryllus eve (Gb'eve) is expressed as stripes in each of the prospective gnathal, thoracic, and abdominal segments and as a broad domain in the posterior growth zone. Dynamics of stripe formation vary among Gb'eve stripes, representing one of the three modes, the segmental, incomplete pair-rule, and complete pair-rule mode. Furthermore, we find that RNAi suppression of Gb'eve results in segmentation defects in both anterior and posterior regions of the embryo. Mild depletion of Gb'eve shows a pair-rule-like defect in anterior segments, while stronger depletion causes a gap-like defect showing deletion of anterior and posterior segments. These results suggest that Gb'eve acts as a pair-rule gene at least during anterior segmentation and also has segmental and gap-like functions. Additionally, Gb'eve may be involved in the regulation of hunchback and Krüppel expression. Comparisons with eve functions in other species suggest that the Gb'eve function may represent an intermediate state of the evolution of pair-rule patterning by eve in insects.

Amino Acid Sequence↗
PubMed1998

Effects of propanolol in patients entered in the Beta-Blocker Heart Attack Trial with their first myocardial infarction and persistent electrocardiographic ST-segment depression.

OBJECTIVE/BACKGROUND: It has been shown that patients with an acute myocardial infarction and persistent electrocardiographic ST-segment depression are at high risk for subsequent cardiac events. The purpose of this retrospective analysis was to examine the long-term effects of propranolol therapy in patients with their first acute myocardial infarction and persistent electrocardiographic ST-segment depression. METHODS: The outcomes of 2877 patients enrolled in the Beta-Blocker Heart Attack Trial (BHAT) with their first myocardial infarction (75% of patients in BHAT) were reviewed. Patients were divided into three groups on the basis of presence or absence of > or =1 mm ST-segment depression in two contiguous leads of the 12-lead electrocardiogram obtained soon after admission or at the time of randomization, which occurred 10.1+/-3.5 days after the index myocardial infarction. Group 1 included 774 patients (392 randomly assigned to placebo and 382 to propranolol) with no ST-segment depression; group 2 included 1447 patients (713 placebo, 734 propranolol) with ST-segment depression at admission or at the time of randomization (labeled as transient); and group 3 included 656 patients (339 placebo and 317 propranolol) who had electrocardiographic ST-segment depression from the time of admission to the time of randomization (labeled as persistent). RESULTS: In group 3, patients with persistent electrocardiographic ST depression, the mortality rate in patients randomly assigned to placebo was 13.6% compared with 7.6% in patients with propranolol (p = 0.012; log rank test). Sudden death in the placebo arm was 9.7% compared with 4.7% in the propranolol group (p = 0.012, log rank test). The results of the Cox regression analysis, adjusting for all baseline variables with p values <0.25, showed the relative risk of overall mortality rate and the relative risk of sudden death were 2.13 ( 1.22, 3.70) and 2.56 (1.27, 5.26), respectively, for the placebo group compared with the propranolol group. Patients with persistent ST-segment depression had the greatest benefit from propranolol (47.2 fewer events [deaths/reinfarctions] per 1000 person-years compared with 78 and 2.1 fewer events in patients with transient and no ST-segment depression, respectively). CONCLUSIONS: It appears that the greatest benefit for beta-blocker therapy in patients after myocardial infarction is observed in patients with persistent ST-segment depression who are at greatest risk for death and reinfarction. Definitive conclusions regarding therapy with beta-adrenergic blocking agents in patients with persistent ST-segment depression cannot be made because our analysis, given its retrospective nature, is only hypothesis generating.

Adrenergic beta-Antagonists↗